Multilayer shielding ring for a flight driving mechanism

ABSTRACT

A shielding ( 6 ) of a turbine housing ( 3 ) of an aircraft engine against radial escape of blade fragments, especially for a high-speed low-pressure turbine, is characterized in that the shielding ( 6 ) is embodied as a rigid ring-shaped component of several layers ( 8 ). Through the decoupling of the containment function from the design of the turbine exhaust gas channel, which is fabricated as a cast part, the disadvantages of the prior art are avoided. Particularly, the design of the turbine exhaust gas channel can be carried out in a cost- and weight-optimized manner.

The invention relates to a shielding of a turbine housing or casing ofan aircraft engine against the radial escape of blade fragmentsaccording to the preamble of the patent claim 1.

In conventional low-speed low-pressure turbines, the so-calledcontainment protection, i.e. the shielding of the housing or casingagainst possible radially outwardly ejected blade parts or bladefragments, is to be examined in connection with the designing of thehousing. Especially for the connection of the low-pressure turbine (LPT)onto the turbine exhaust gas housing or casing (Turbine Exhaust CaseTEC), which is generally embodied as a cast part, often only anexamination of the wall thickness is necessary. This examinationgenerally determines that the wall thickness of the connection LPT/TECis sufficiently strongly dimensioned also as a containment protection.

Such a shielding from the prior art is shown in a cutaway portion viewin FIG. 2. Thereby the low-pressure turbine 1 is shown with turbineblades 2, which are arranged within a turbine housing or casing 3.Thereby the turbine blades are arranged axially after a compressor thatis not shown and a combustion chamber that is not shown, and are locatedon a turbine disk that rotates about the engine axis. The turbinehousing 3 is connected via a flange 5 with the turbine exhaust gaschannel 10. The turbine exhaust gas channel 10 of the prior art isembodied as a cast part, which also comprises a containment function dueto the existing material thickness. That is to say, in the unlikely caseof an engine damage with loss of turbine blades or blade parts, theturbine exhaust gas channel with containment function serves to preventthe escape of the blade parts out of the engine housing and thereby toavoid possible damages of the aircraft airframe. In FIG. 2, the impactarea that is determinative for the design is identified by the straightlines enclosing an angle α.

For achieving the required specifications, future engine concepts needlow-pressure turbines with high AN², high turbine inlet temperatures,and a compact short structure.

In high-speed low-pressure turbines for such modern engine concepts, thecontainment protection is, however, a particular design criterium,because the regular cast part thickness of the turbine exhaust gaschannel is no longer sufficient to prevent a possiblethrough-penetration of loose blade parts due to the higher momentum ofthe blade parts. Therefore, according to the present state, nomaterial-, cost- and weight-optimized low-pressure turbine/turbineexhaust gas channel (LPT/TEC) connection is possible. Rather, thematerial selection and material thickness of the LPT/TEC connection isdetermined by the required containment thickness and not by theoptimized LPT/TEC connection. The material selection is also determinedby the higher requirements for the cast material in the containment areaand is thereby made more expensive.

Nonetheless, a containment solution in the area of the low-pressureturbine is known from the U.S. Pat. No. 5,328,324. Therein a glass fiberwoven hose is proposed, which is laid onto a carrier element in amultiply-folded configuration, quasi as a collar, whereby the carrierelement is located on the outer side of the turbine housing above thelow-pressure turbine. In that regard, the glass fiber woven material isproduced from a continuous fiber and is heat resistant. The intactnessof the continuous fiber is decisive for the functioning of thiscontainment protection. The glass fiber woven hose is therebydimensioned so that it lies tightly on the carrier element. However,here no special solution for the low-pressure turbine/turbine exhaustgas channel connection is presented. Disadvantageous in this solution,on the one hand, is the unfixed construction of the collar, which ishighly sensitive to external influences, for example mechanicalinfluences, moisture, etc. It is a further disadvantage that damages ofthe continuous fiber of the glass fiber woven hose are not easilynoticed and can lead to a total failure of the containment protection incase of need.

Therefore, it is the underlying object of the invention to avoid thedisadvantages of the known solutions of the prior art, and to makeavailable an improved solution for a containment protection on theLPT/TEC connection especially of high-speed low-pressure turbines.

This object is achieved according to the invention by a multilayershielding for an aircraft engine with features of the patent claim 1.Advantageous embodiments and further developments of the invention areset forth in the dependent claims.

The inventive shielding of a turbine housing of an aircraft engineagainst radial escape of blade fragments, especially for a high-speedlow-pressure turbine, is characterized in that the shielding is embodiedas a rigid ring-shaped component of several layers. Thereby thering-shaped shielding can be arranged radially within or outside of theturbine housing. In connection with mounting on the turbine housing, theshielding can also direct cooling air, for example from the fan streamflow, in a targeted manner onto the outer skin of the housing. It isfurther possible that the ring-shaped shielding consists of severalsegments, whereby production and assembly are simplified. Due to thestiff embodiment, the shielding is protected against externalinfluences, and can be embodied in a self-supporting manner.

An advantageous embodiment of the inventive shielding provides that theshielding is arranged on the turbine exhaust gas channel. By thedecoupling of the containment function from the design of the turbineexhaust gas channel, which is fabricated as a cast part, thedisadvantages of the prior art are avoided. Especially the design of theturbine exhaust gas channel can be carried out in a cost- andweight-optimized manner, i.e. more-economical materials and materialthicknesses can be utilized here, in comparison to what would be thecase with an integrated containment function. The containment functionis then exercised alone by the ring-shaped multilayer shielding.

An advantageous embodiment of the inventive shielding provides that theshielding is embodied as a forged component. This makes possible amultilayer construction with selection of suitable material layers. Inthat regard, on the one hand the strength is a defining factor, as wellas the temperatures present in the area of the low-pressure turbine onthe housing or on the LPT/TEC connection. In that regard, thepossibility of the temperature expansion is to be taken into account fora shielding ring having multiple parts in the circumferential direction.

A further advantageous embodiment of the inventive shielding providesthat the shielding is arranged within the turbine housing. On the onehand this avoids interfering additional structural components outside ofthe turbine housing, and on the other hand it is hereby prevented thatthe housing or the LPT/TEC connection is penetrated through in the caseof a blade damage, whereby the costs of an engine failure rise further.

Still another advantageous embodiment of the inventive shieldingprovides that the shielding is embodied as a flow guide element. Thiscan be the case both for the application of the shielding within oroutside of the housing. Thereby additional flow guide elements can beapplied on the shielding, or alternatively the shielding itself isformed or mounted in a flow-advantageous manner.

Still a further advantageous embodiment of the inventive shieldingprovides that the shielding is embodied as a heat shield. This isespecially necessary for the installation in the flow channel, i.e.within the turbine housing. However, this can also be suitable for thepurpose for installation on the outer circumference of the turbinehousing, in order to prevent injuries due to burns on hot enginecomponents during maintenance work.

An advantageous embodiment of the inventive shielding provides that thelayers are constructed of different materials. For example, highly heatresistant forgeable alloys come into consideration as materials. Therebythe strength characteristics, temperature expansion and weight of theshielding can be influenced to the desired extent. This is especiallyexpedient in the sense of a weight- and cost-optimization.

An advantageous embodiment of the inventive shielding provides that thelayers comprise different thicknesses. Like the material selection, thestrength and the weight of the shielding can also be optimized by theselection of the layer thickness, and thereby the costs of the componentcan be reduced.

An advantageous embodiment of the inventive shielding provides that thelayers are adapted or tuned to one another in a vibration-optimizedmanner. Thereby the layers of the multilayer shielding ring areconnected in a resonance-free manner in the shielding housing. Herebyboth the vibration characteristics of the shielding alone, as well asthe vibration characteristics of the components coupled with theshielding, can be taken into consideration. Furthermore, the variationof the vibration characteristics due to fluid flow thereon andtemperature expansion can be taken into consideration in the design andadaptation or tuning of the layers.

Finally an advantageous embodiment of the inventive shielding providesthat the shielding comprises an enclosure or mounting frame fordifferent functional layers. In that regard, enclosure or mounting framecan also encompass a shielding housing with which different layers areconnected in a joint-technical manner. In that regard, the ring-shapedlayers can be encased or enclosed or surrounded quasi from three sides,and if applicable can also be received in a floating manner in themounting frame.

Further measures improving the invention are explained more closely inthe following together with the description of a preferred exampleembodiment of the invention in connection with the figures. It is shownby:

FIG. 1 an advantageous embodiment of the present invention,schematically in a cutaway portion;

FIG. 2 a schematic partial sectional illustration of a shielding of theprior art.

In the depicted figures, the same or similar components are identifiedwith the same reference numbers. Direction indications refer to the axesof the aircraft engine.

FIG. 1 schematically shows in the manner of a cutaway portion, anadvantageous embodiment of an inventive shielding 6 on a high-speedlow-pressure turbine 1. In that regard, the compressor which is notshown in the drawing and the combustion chamber, as well as the high-and medium-pressure turbine which is similarly not shown, are located inthe drawing plane on the left hand side, that is to say upstream withregard to the flow. Thereby the FIG. 1 shows a cutaway portion of ahalf-section.

In FIG. 1, a part of a turbine blade 2 is illustrated, which is arrangedwithin a turbine housing 3 that surrounds the turbine stage in thecircumferential direction. The turbine housing 3 is connected with theturbine exhaust gas channel 4 or connected thereto via amaterial-technically optimized flange connection 5.

The shielding 6 is arranged on the connection of the low-pressureturbine 1 to the turbine exhaust gas channel 4 within the turbinehousing 3. A flange 9 protrudes inwardly in the radial direction on theturbine exhaust gas channel 4, and the shielding 6 or the shieldinghousing 7 is flange-connected on the flange 9.

The shielding 6 or the containment ring, which is illustrated L-shapedin section and is ring-shaped in the circumferential direction, isembodied as a multilayer forged part in the present example embodiment.In that regard, the two layers 8 of the shielding 6 are received in ashielding housing 7 and are connected therewith in aforging-technological manner. Both the type of the alloy as well as thelayer thickness/number of layers differ from one another in the twolayers 8 shown in the example embodiment. In that regard, theresonance-free shielding 6 in the present example embodiment alsocomprises integrated heat-shield and flow-guiding function in additionto the containment function. The containment function is presently notintegrated in the connection of low-pressure turbine 1/turbine exhaustgas channel 4, whereby this connection can be embodied as aweight-optimized cast part.

The invention is not limited in its embodiment to the preferred exampleembodiment set forth above. Rather, a number of variants is conceivable,which also makes use of the solution claimed in the patent claims, alsoin embodiments of a different type.

1. Shielding (6) of a turbine housing (3) of an aircraft engine againstradial escape of blade fragments, especially for a high-speedlow-pressure turbine (1), characterized in that the shielding (6) isembodied as a rigid ring-shaped component of several layers (8). 2.Shielding (6) according to patent claim 1, characterized in that theshielding is arranged on the turbine exhaust gas channel.
 3. Shielding(6) according to patent claim 1, characterized in that the shielding (6)is embodied as a forged component.
 4. Shielding (6) according to patentclaim 1, characterized in that the shielding (6) is arranged within theturbine housing (3).
 5. Shielding (6) according to patent claim 1,characterized in that the shielding (6) is embodied as a flow guidingelement.
 6. Shielding (6) according to patent claim 1, characterized inthat the shielding (6) is embodied as a heat shield.
 7. Shielding (6)according to patent claim 1, characterized in that the layers (8) aremade of different materials.
 8. Shielding (6) according to patent claim1, characterized in that the layers (8) comprise different thicknessesand/or numbers. 9-10. (canceled)
 11. Shielding (6) according to patentclaim 1, characterized in that the layers (8) are tuned to one anotherin a vibration-optimized manner.
 12. Shielding (6) according to patentclaim 1, characterized in that the shielding (6) comprises a mountingframe (7) for different functional layers.